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Need for speed!!

Old 09-11-2010, 08:59 PM
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Default Need for speed!!

A different angle here...OK, I have many designs...most are conventional power systems and I have come to like the 24 and 20 gram motors and have a few 9 gram and 5 gram ones around.. I have built a few very light projects with one and 2 cell and larger props... but now I am going the other direction

I seen a F5D pylon racer do over 200 MPH+ with a 4.5x4.5 prop 2400 mah 4s and what seems to be a ducted fan motor (NEU) on just a prop/spinner

Now my question. I understand its watts that will destroy a motor.. and if one hold down the prop size, then one could up the voltage as long as it stayed under the rated watts.

The reason for the elevated voltage is for higher rpms which on a very, very sleek/light plane should translate to higher speed. I'm looking at 4 and 5 cell 100 mah or 240 mah packs.

Has anyone ever tried this idea?... example take a 20 gram motor and use maybe a 3" prop, increasing the pitch by heating prop carefully and move it up to maybe 5.0 or 6.0 pitch. I have custom designed 5 inch cox grey props before and had great success in the 70's. Maybe there's a good source for extreme precision micro speed props.

Might be the standard pitch could be used if the rpms are high enough..

I'm looking for 30,000 rpm .

Is this achievable by merely upping the volts with caution not to get the watts to the danger point?

All this could translate to a new class of micro pylon racer...doing maybe 150+ mph..
Old 09-14-2010, 10:48 AM
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Default RE: Need for speed!!

gittarpikk- I have been fooling around with electric pylon planes for about a year now. I scratch build balsa 400 sized planes that are fiberglassed then I put crazy motors in them[X(] One of my planes was traveling between 140 and 150mph. Then to take a break I switched to EDF's for a while.

In my experience over the past year or so I have found (could be wrong) that watts are a measurement of power. It appears that amps and voltage (higher) than what the motor, ESC , or battery are designed for, cause failures of one or more of the components (the weak link fails first). I have burned up ESC's, motors, and batteries during this learning curve and even though I AM NOT an electrical expert have gained some valuable experience through my
losses[:@].

Also the smaller the airframe the more difficult it becomes to STUFF[&:] a battery inside that will handle the amps and give more than two or three minutes of flight time. I've experimented with this as well.

One thing I forgot to mention. My planes are 27" wing span and they are EXTREMELY hard to keep up with at speeds above 100 to 120. A smaller span and size doing the same speeds would be even more difficult. Trust me I got eyes like a hawk and most of the club guys have told me they could not fly my planes because they can't see them. Just something to consider. The size 27" I am flying now is at my threshhold for seeing and controlling. Also as speeds go up so must the strength of the airframe and to strengthen the airframe you add weight and size (and you have this unending circle). But hey experimentation is fun!

I would like to help out but I am not sure what you are looking to do. What type of plane are you looking at and what type of power systems. I am not sure what you mean 24 and 20 gram motors? How many watts (max) do those motors put out.

Please don't think I am trying to discourage you.....man, I am with guys that think outside the RC box. I'm not one of these OGG's (old grouchy guys) that lurk around these forums. Just trying to think it through with you...with some crash and burn experience. Hey, I'm up for a joint build, if it can be made to work! Skip
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Old 09-14-2010, 05:35 PM
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Default RE: Need for speed!!

Hi Skip

I have a couple real good guys local working on this as well... So we're not alone..

One is at a model show and will be back next Thurs and the other will get started this winter on his version

I understand watts = performance as well as extra heat etc...and there was a sort of formula I seen somewhere on the weight of motor (motor body mass)is exponential to amount of watts it can safely handle. But at higher speeds, and more effieciency watts converted better to work (BHP) then maybe the speed can increase on same watts with less damage due to heat...

I am beginning to see the EDF motors may be the ticket however they are somewhat heavy and all are in 28 mm diameter...making the fuse required to be 30MM...which doesn't help much on frontal area but works for stuffing larger batteries inside.,

Your planes look "right down the alley" of the direction I plan to take but I was hoping for about half the diameter. Maybe I'm dreaming but was hoping for the lower frontal area as that is where the gain must be to reach the objectives.. Looks like I will have to turn my own spinners IF I can find a smaller diameter edf motor that can "hang in there" in a real tough environment...yet be affordable.
Old 09-14-2010, 06:11 PM
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Default RE: Need for speed!!

I have given this some thought this afternoon and your post confirms what I have been thinking.
Some of the EDF "inrunners" in the 20 to 24mm size range are close but I can't find one that weighs less than 50grams. They have the power to put a small missle into orbit[X(] but the airframe has to be right.
For me...cost is a factor[] that is why I have been scratch building from balsa with a fiberglass covering. My 140mph plane weighs about 16oz ready to scream and the airframe only costs me about 25 to 30 bucks. It is called a Slipso 400 and was designed by Paul Daniels the plans are free and can be downloaded for free online. Short kits are also sold by Mountain Models. There is a great build thread on RC Groups on the design.
I downsized for one of my builds (100% to 90%) and found that the smaller size became a real issue with stuffing a battery (1800mah/30C/ 3S) 80amp ESC (pulling over 60amps WOT), and two servos that are able to withstand the forces that 150mph bring.
The Great Planes "Rifle" is close and takes a 24mm and smaller motor. But I have heard that they are snapping the wings off at 120mph. ( They have made some recent improvements with the design)
Guys have tried planes just like mine made with Depron and when pushed the airframes eventually fail.
Another thing that I ran into with downsizing my planes smaller and "lighter" is that they become less flyable at the higher speeds and are very pitch sensitive and sensitive to the winds aloft. My 90% plane is less fun to fly than my 100% which is 100grams heavier.
To go half the diameter the fuz would have to be hollow molded out of carbon/kevlar or glass. I sure wish I had the skills to hollow mold but I haven't gotten that far yet (have been doing alot of reading though).
Old 09-14-2010, 08:02 PM
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Default RE: Need for speed!!

Thanks for the reply

One method that works well for "one of" designs is a glassing method called "Lost foam technique"

Use pink foam or blue foam , turning it to shape then glass over with a light glass cloth ...maybe 2 layers then spray or squirt something in to disolve the foam and what you have left is the glass hull.

IMO, I would think that little weight would not hurt speed if the final diameter is considerably less than a fuse that has a 30mm spinner.I feel 18-20mm is the target diameter and if it can be made to stay together, a 1/8 or 3/16 thick wing


Old 09-14-2010, 10:48 PM
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Default RE: Need for speed!!

http://www.allerc.com/product_info.p...oducts_id=3202

Interesting little motor lots of power on 3S with a 3x2 prop.
134watts at 34,500rpm (need a good prop though, carbon)

Check this out: http://www.fesselflug.ch/werkstatt/m...ed-catfish.php
Check out the video....I'd like to get my hands on that prop and motor. They are using an outrunner...(might be a Scorpion). I use helicopter outrunners (high KV) on my speed planes as well.
Old 09-15-2010, 05:51 AM
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Default RE: Need for speed!!

Hi, Thanks for reply...and links

Althought I didn't translate the page, I could tell the motor wasa a powerhouse....but looks a little heavy for this app.... the vid says it all... was that an esc, or lipo puff at the end?...it was sure fast
Old 09-15-2010, 09:08 AM
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Default RE: Need for speed!!

That was the ESC going. The Germans are the fastest guys in the world when it comes to electric speed planes. I would love to fly over there for the Speed Cup event that they have each year. The planes are nitro and electric and are the Worlds cutting edge.
Old 09-21-2010, 10:41 AM
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Default RE: Need for speed!!

I started on a new plane yesterday somewhat along the lines you mentioned but not that small. the sides are cut out and I need to head to the LHS to get some 1/4 triangle stock. It will get a 2445-2900 inrunner. It is a modification of the Slipso 400 design. The nose will be 40mm longer to help with balance and give a bit move room to STUFF in all the gear. This one will get a small folding prop setup. The folder will keep the motor shaft from getting bent on landing and the Turbo design of the spinner will allow air to get into the motor. Wingspan will be about 27". Hope to keep the weight below 500grams this time.
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Old 11-18-2010, 08:49 PM
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Default RE: Need for speed!!

I hae a 40 size Estralleta that had an OS VR engine (50" wingspan) I am looking for an electric conversion to make this thing a rocket ship. Are EDF's the answer? FYI, I was turning an 8X6 wood propeller with nitro. Can anyone give me a suggestion on motor/esc/lipo setup?
Old 12-11-2010, 07:25 AM
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